Adding large submenues menus on Wordpress - nightmarew solved

Add this to wp-admin/nav-menus.php :        

<style type="text/css">
            .munevera {
                display:block;
            }
.categorydiv div.tabs-panel, .customlinkdiv div.tabs-panel, .posttypediv div.tabs-panel, .taxonomydiv div.tabs-panel, .wp-tab-panel {
    max-height: 400px;
}
.menu-item-bar .menu-item-handle {
    padding: 5px 15px;
}
.menu-item-bar {
    margin: 3px 0 0;
}
div#side-sortables {
    position: fixed;
    top: 250px;
    left: 180px;
width: 300px;
}
            </style>